- Literature Survey
- Objectives of the Work
- Mild steel and zinc are most widely used engineering materials especially for structural applications.
- They are exposed to various aggressive environments during their usage and hence undergo corrosion.
- Corrosion of steel and zinc materials and their protection have become fundamental, academic and industrial concern
- The corrosion of metals received a prime attention of scientists since it has many serious consequences including economic, health, safety, technological and cultural consequences all over the world.
- If economic loss alone is considered, the costs associated with corrosion can be estimated with reasonable accuracy. The typical estimations were US $275 billion dollars in1998 and US$364 billion dollars in 2005, draining about 3.1% of the GDP from the US economy [1-6].
- These numbers alone justify much greater need for development of effective corrosion protection techniques
- Various methods have been employed in controlling their corrosion. The use of chemical inhibitors is one of the best practical methods in controlling the corrosion.
- Various types of chemical inhibitors like organic and inorganic compounds, pharmaceuticals drugs, dyes and even plant extracts are developed to control corrosion.
- But the practice of corrosion inhibition is greatly influenced by new regulations that have been developed to check the use of toxic compounds and environmental damage resulting from the use of such compounds.
- Hence there is a trend to replace some widely used inhibitors such as chromates and cyanides because of their toxicity, environmental damage and pollution caused by these chemicals.
- Although many organic inhibitors were developed as corrosion inhibitions for mild steel and zinc, a little work has been done in detecting and using electro active compounds such as dyes, drugs and natural extracts as corrosion inhibitors for steel and zinc.
- The aim of the present proposal is to find the new class of non toxic inhibitors for controlling the corrosion of steel and zinc in acidic medium and establish the mechanism of corrosion by analytical and theoretical methods.
- Mild steel has been extensively used under different conditions in chemical and allied industries in handling alkaline, acid and salt solutions. Chloride, sulphate and nitrate ions in aqueous media are particularly aggressive and accelerate corrosion. One way of protecting mild steel from corrosion is to use corrosion inhibitors. Most of the well-known inhibitors are organic compounds containing nitrogen, sulphur and/or oxygen atoms. It has been observed that most of the organic inhibitors act by adsorption on the metal surface [8 - 12].
- Zinc is a metal with numerous industrial applications and is mainly used for the corrosion protection of steel. The dissolution behavior of zinc in acidic and nearly neutral media is known to be inhibited by nitrogen and sulfur-containing organic compounds. Such compounds contain electron-donating groups that decrease the corrosion rate by increasing the hydrogen over voltage on the corroding metal. Studies of the effect of organic additives on the corrosion rate of zinc have been the subject of many investigators. The efficiency of aldehydes and amino acids as inhibitors of corrosion for different metals in different corrosive environments has been studied by several workers, and their inhibition efficiency is due to the formation of a protective layer or film on the metallic surface. The role of this film is to isolate the corroding metal from the corrosive medium [13-25].
- Many works have been done for controlling the corrosion of steel and zinc metals in acidic and neutral medium some of them are discussed below
• The corrosion inhibition of mild steel in 0.5 M hydrochloric acid solutions by some new hydrazine carbodithioic acid derivatives namely N0-furan-2-ylmethylene- hydrazine carbodithioic acid (A), N0-(4-dimethylaminobenzylidene)- hydrazinecarbodithioic acid (B) and N0-(3-nitro-benzylidene)- hydrazine carbodithioic (C) was studied. The inhibition efficiency obtained by these compounds is increased by increasing their concentration. The inhibition efficiency follow the order C > B > A. Polarization studies show that these compounds act as mixed type inhibitors in 0.5 M HCl solutions. .